Younger brother of former Munster player Ultan, he played on an Ireland Schools side that included Brian O’Driscoll.

O’Callaghan won an U19 World Cup medal in 1998, that side coached by Declan Kidney. Made his U21 debut in Feb ’99 and since then has played at every international level.

Featured in both the 2006 & 2008 Heineken Cup winning sides, and in 2009 went on his second trip with the British & Irish Lions captaining the side to victory over the Southern Kings in Port Elizabeth.

Signed a contract extension late in 2013 that will keep him at Munster until at least 2016.

Became Munster's record appearance holder when he came off the bench to win his 241st cap against Zebre at Musgrave Park in February 2014.

The first ever recipient of IRUPA's Contribution to Society Award in recognition of the significant impact made to society through his work with Unicef.

Represented the Barbarians in June 2014, the Baa-baas defeating an England XV 23-39 at Twickenham.

Munster's most capped player won a further 17 caps for the province in Season 14/15.